Patent application title: HIGH ACTIVITY HYDRODESULFURIZATION CATALYST, A METHOD OF MAKING A HIGH ACTIVITY HYDRODESULFURIZATION CATALYST, AND A PROCESS FOR MANUFACTURING AN ULTRA-LOW SULFUR DISTILLATE PRODUCT

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Abstract:

A method of making a high activity catalyst composition suitable for use
in the hydrodesulfurization of a middle distillate feed, such as diesel
fuel, having a high concentration of sulfur, to thereby provide a low
sulfur middle distillate product. The method comprises heat treating
aluminum hydroxide under controlled temperature conditions thereby
converting the aluminum hydroxide to gamma-alumina to give a converted
aluminum hydroxide, and controlling the fraction of converted aluminum
hydroxide that is gamma-alumina. A catalytic component is incorporated
into the converted aluminum hydroxide to provide an intermediate, which
is heat treated to provide the high activity catalyst composition. The
high activity catalyst composition can suitably be used in the
hydrodesulfurization of a middle distillate feed containing a high sulfur
concentration.

Claims:

1. A method of making a catalyst composition suitable for use in the
manufacture of ultra low sulfur diesel, said method comprises: forming a
shaped particle comprising at least 90 weight percent, exclusive of
water, boehmite; calcining said shaped particle under a controlled
temperature condition to convert said boehmite of said shaped particle to
gamma-alumina; controlling said controlled temperature condition to
within a calcination temperature range of from about 850.degree. F. and
950.degree. F. so that a substantial portion of said boehmite of said
shaped particle is converted to a crystalline transitional phase of
alumina but less than a material amount of said boehmite of said shaped
particle is converted to a crystalline transitional phase other than
gamma-alumina to thereby provide a calcined shaped particle; impregnating
said calcined shaped particle with a hydrogenation catalytic component to
thereby provide an impregnated calcined shaped particle; and calcining
said impregnated calcined shaped particle to thereby provide said
catalyst composition.

2. A method as recited in claim 1, wherein said calcined shaped particle
has a material absence of both boehmite and a crystalline transitional
phase of alumina other than gamma-alumina.

3. A method as recited in claim 2, wherein said calcined shaped particle
contains less than 5 weight percent boehmite with the weight percent
being based on the total weight of said calcined shaped particle.

4. A method as recited in claim 3, wherein less than 5 weight percent of
said alumina of said calcined shaped particle is said transitional
crystalline phase of alumina other than gamma alumina.

5. A method as recited in claim 4, wherein the median pore diameter of
said calcined shaped particle is in the range of from about 80 angstroms
to about 110 angstroms, wherein the total pore volume of said calcined
shaped particle is in the range of from about 0.6 cc/gram to about 1.1
cc/gram, and wherein more than 70 percent of the total pore volume of
said calcined shaped particle is contained in the pores having a pore
diameter of from 80 angstroms to 350 angstroms.

6. A method as recited in claim 5, wherein said hydrogenation catalytic
component is selected from the group of consisting of molybdenum
compounds, cobalt compounds, nickel compounds, phosphorous compounds, and
any combination of one or more of such compounds.

7. A method as recited in claim 6, wherein said calcining of said
impregnated calcined shaped particle is conducted so that the at least 90
weight percent of the alumina of the resulting said catalyst composition
is in the crystalline transitional phase of gamma alumina and less than 5
weight percent of the alumina of said catalyst composition is in the
crystalline transitional phase other than gamma alumina.

8. A method as recited in claim 7, wherein said catalyst composition is
characterized as having a median pore diameter in the range of from about
80 angstroms to about 110 angstroms, a total pore volume in the range of
from about 0.6 cc/gram to about 1.1 cc/gram, and more than 70 percent of
said total pore volume that is contained in the pores having a pore
diameter of from 80 angstroms to 350 angstroms.

9. A method as recited in claim 8, wherein said catalyst composition
further comprises a molybdenum compound in the range of from about 2 to
about 10 weight percent, calculated as molybdenum trioxide, a cobalt
compound in the range of from about 0.01 to about 10 weight percent,
calculated as cobalt oxide, and a phosphorous compound in the range of
from about 0.01 weight percent to about 5 weight percent, calculated as
phosphorous.

10. A process for making an ultra low sulfur diesel product, wherein said
process comprises: contacting, under hydrodesufurization conditions, a
diesel feedstock, wherein said diesel feedstock comprises a first sulfur
concentration, with a catalyst comprising a calcined impregnated shaped
support, wherein said shaped support of said impregnated shaped support
has a material absence of aluminum hydroxide and a material absence of
crystalline transitional phase of alumina other than gamma-alumina prior
to the impregnation thereof with a hydrogenation catalytic component to
thereby provide said impregnated shaped support thereafter calcined; and
yielding said ultra low sulfur diesel product having a second sulfur
concentration.

11. A process as recited in claim 10, wherein said material absence of
aluminum hydroxide in said shaped support is less than 5 weight percent
of the total weight of said shaped support and wherein said material
absence of said crystalline transitional phase of alumina other than
gamma alumina in said shaped support is less than 5 weight percent of the
total weight of said shaped support.

12. A process as recited in claim 11, wherein said material absence of
said crystalline transitional phase of alumina other than gamma alumina
is less than 2 weight percent of the total weight of said shaped support.

13. A process as recited in claim 12, wherein said material absence of
said crystalline transitional phase of alumina other than gamma alumina
is less than 1 weight percent of the total weight of said shaped support.

14. A process as recited in claim 13, wherein said hydrogenation
catalytic component in said catalyst composition includes a molybdenum
compound in the range of from about 3 to about 30 weight percent,
calculated as molybdenum trioxide, a cobalt compound in the range of from
about 0.01 to about 10 weight percent, calculated as cobalt oxide, and a
phosphorous compound in the range of from about 0.01 weight percent to
about 5 weight percent, calculated as phosphorous, wherein the weight
percents are based on the total weight of said catalyst composition.

15. A process as recited in claim 14, wherein said catalyst composition
is characterized as having a median pore diameter in the range of from
about 80 angstroms to about 110 angstroms, a total pore volume in the
range of from about 0.6 cc/gram to about 1.1 cc/gram, and more than 70
percent of said total pore volume that is contained in the pores having a
pore diameter of from 80 angstroms to 350 angstroms.

16. A process for making an ultra low sulfur diesel product, wherein said
process comprises: contacting, under hydrodesufurization conditions, a
diesel feedstock, wherein said diesel feedstock comprises a first sulfur
concentration, with a catalyst comprising a calcined impregnated shaped
support, wherein said shaped support of said impregnated shaped support
comprises, prior to its impregnation and calcination, at least 90 weight
percent alumina that is in the crystalline transitional phase of
gamma-alumina, less than 5 weight percent alumina that is in the
crystalline transitional phase of delta-alumina, and less than 5 weight
percent alumina that is in the crystalline transitional phase other than
gamma-alumina and delta-alumina, and wherein said shaped support has
incorporated therein a hydrogenation catalytic component thereby
providing said impregnated shaped support, and wherein said impregnated
shaped support is calcined; and yielding said ultra low sulfur diesel
product having a second sulfur concentration.

17. A process as recited in claim 16, wherein said catalyst includes less
than 2 weight percent alumina that is in the crystalline transitional
phase other than gamma alumina.

18. A process as recited in claim 17, wherein said catalyst includes less
than 1 weight percent alumina that is in the crystalline transitional
phase other than gamma alumina.

19. A process as recited in claim 18, wherein said hydrogenation
catalytic component in said catalyst composition includes a molybdenum
compound in the range of from about 3 to about 30 weight percent,
calculated as molybdenum trioxide, a cobalt compound in the range of from
about 0.01 to about 10 weight percent, calculated as cobalt oxide, and a
phosphorous compound in the range of from about 0.01 weight percent to
about 5 weight percent, calculated as phosphorous, wherein the weight
percents are based on the total weight of said catalyst composition.

20. A process as recited in claim 19, wherein said catalyst composition
is characterized as having a median pore diameter in the range of from
about 80 angstroms to about 110 angstroms, a total pore volume in the
range of from about 0.6 cc/gram to about 1.1 cc/gram, and more than 70
percent of said total pore volume that is contained in the pores having a
pore diameter of from 80 angstroms to 350 angstroms.

[0002] This invention relates to a catalyst and process for the
manufacture of a hydrocarbon product having a low sulfur concentration.
The invention further relates to a high activity hydrodesulfurization
catalyst, a method of making such high activity hydrodesulfurization
catalyst, and a process for manufacturing diesel distillate product
having a low sulfur concentration using the high activity
hydrodesulfurization catalyst.

[0003] U.S. Environmental Protection Agency regulations are currently
targeting for the year 2006 a limitation on the maximum sulfur
concentration in on-road diesel of 15 parts per million (ppm). The
European Union will limit the sulfur concentration in diesel fuel
starting in the year 2005 to less than 50 ppm. Other organizations are
supporting even stricter requirements of as low as 5 to 10 ppm sulfur in
diesel. With the current hydrodesulfurization technology, the ability to
produce such a low sulfur diesel product is a real challenge, and there
are ongoing efforts to develop improvements in the existing
hydrodesulfurization technology that will permit the economical
hydrodesulfurization of a sulfur-containing diesel feed stream to yield
an ultra-low sulfur diesel product.

[0004] A conventional hydrodesulfurization process employed to reduce the
concentration of organosulfur compounds contained in a hydrocarbon
feedstock is typically carried out by contacting the hydrocarbon
feedstock with a hydrotreating catalyst in the presence of hydrogen and
at an elevated temperature and pressure. A typical hydrotreating catalyst
contains a group 6 metal component, such as molybdenum, and a group 9 or
group 10 component, such as cobalt or nickel, supported on a refractory
oxide support.

[0005] One early patent, U.S. Pat. No. 3,669,904, discloses a method of
making a gas oil hydrodesulfurization catalyst prepared from a precursor
mixture of mildly calcined boehmite and uncalcined boehmite The disclosed
method addresses certain of the disadvantages and limitations with the
use of technical grade boehmite in forming extruded pellets for use in
making certain catalysts. The gamma alumina pellets are made by mixing a
mildly calcined technical grade boehmite with uncalcined technical grade
boehmite and an extrusion aid followed by forming a pellet that is
calcined.

[0006] U.S. Pat. No. 3,853,789 discloses a method of making a mechanically
strong alumina extrudate that may be used as a catalyst carrier. The
extrudate is prepared by mixing with water specific proportions of gamma
alumina powder having a certain particle size and alumina monohydrate
(boehmite) having a certain particle size to form an extrudable paste
from which an extrudate is formed. The extrudate is dried and then
heat-treated at temperatures of 1150 to 1250° F.

[0007] U.S. Pat. No. 4,066,574 discloses a catalyst for use in the
hydrodesulfurization of a heavy oil feedstock. The catalyst is an alumina
support that is impregnated with Group VIB and Group VIII metals or metal
compounds. The alumina support has a specific pore structure that
provides for certain desired catalyst properties. The alumina support is
made by mixing water and a strong mineral acid with amorphous or
crystalline hydrate alumina powder to form a paste that is extruded. The
density of the extrudate may be controlled by the addition of ammonium
hydroxide to the extrudable paste. The extrudate is calcined at a
temperature of 500° F. to 1600° F. The support has at least
70 volume percent of its pore volume in pores having a diameter between
80 and 150 Angstroms and less than 3 volume percent of its pore volume in
pores having a diameter above 1000 Angstroms.

[0008] U.S. Pat. No. 4,089,811 discloses a method of making an alumina
catalyst support by calcining alpha alumina monohydrate (boehmite) at a
temperature of from about 800° F. to 900° F. to form
calcined alumina containing gamma alumina and mixing the calcined alumina
with water to form a wetted alumina. The wetted alumina at a pH of from 6
to 12.5 is heated to a temperature of from 190° F. to 250°
F. for from 8 to 24 hours to convert the calcined alumina to beta alumina
trihydrate. Maintaining the calcination temperature within the range of
800 to 900° F. is important to achieve the desired results. The
calcined alumina contains at least about 80% gamma alumina with the
remaining portion of the alumina being substantially entirely alpha
alumina monohydrate.

[0009] U.S. Pat. No. 4,271,042 discloses a desulfurization catalyst that
comprises a hydrogenation catalytic component composited with gamma
alumina that contains dispersed delta and/or theta phase alumina. The
catalyst is prepared by precalcining gamma alumina or boehmite at a
temperature of from 1600° F. to 2000° F. to induce the
formation of delta and/or theta phase alumina. The resulting powder is
then mixed with alpha alumina monohydrate (boehmite) and formed into
pellets or extrudates that are calcined at a temperature of from
900° F. to 1400° F. to form a catalyst support consisting
of an intimate mixture of gamma alumina with delta and/or theta phase
alumina. The catalyst support may be composited with the hydrogenation
component.

[0010] U.S. Pat. No. 5,300,217 discloses a hydroprocessing catalyst that
comprises a hydrogenation component supported on a porous, amorphous
refractory oxide containing delta alumina. The finished catalyst contains
greater than 5 weight percent delta alumina. The amorphous, porous
refractory oxide support material is prepared by extruding a precursor of
the desired support, such as a refractory gel, followed by calcination of
the extrudate. To obtain the desired delta-gamma alumina combination for
the support, it is precalcined, prior to impregnation with the
hydrogenation component, at a temperature above about 900° F. and
preferably above 1800° F.

[0011] With the increasingly stricter sulfur concentration requirements
for diesel fuels there is an ongoing need to develop improved catalysts
and processes for the manufacture of the low sulfur diesel fuels.

[0012] It is, thus, an object of the invention to provide an improved
catalyst for use in processes for the manufacture of a distillate product
having a low concentration of sulfur.

[0013] Another object of the invention is to provide a process for making
low sulfur distillate product.

[0014] Thus, in accordance with the invention, provided is a catalyst
composition that comprises a shaped support material having incorporated
therein a catalytic hydrogenation component wherein the shaped support
material is a calcined alumina having a material absence of aluminum
hydroxide and a material absence of crystalline transitional phase of
alumina other than gamma alumina. Another embodiment of the catalyst
composition comprises a calcined impregnated shaped support, wherein the
shaped support of the impregnated shaped support comprises, prior to its
impregnation and calcination, at least 90 weight percent alumina that is
in the crystalline transitional phase of gamma-alumina, less than 5
weight percent alumina that is in the crystalline transitional phase of
delta-alumina, and less than 5 weight percent alumina that is in the
crystalline transitional phase other than gamma-alumina, and wherein the
shaped support has incorporated therein a hydrogenation catalytic
component thereby providing the impregnated shaped support, and wherein
the impregnated shaped support is calcined.

[0015] In accordance with another invention is a method of making a
catalyst composition useful in the manufacture of a low sulfur distillate
product. This method includes providing a shaped support, having a
material absence of aluminum hydroxide and a material absence of
crystalline transitional phase of alumina, comprising gamma-alumina, and
incorporating therein a catalytic component to thereby provide an
intermediate, and calcining the intermediate to thereby provide the
catalyst composition. Another embodiment of the inventive method of
making the catalyst composition includes forming a shaped particle
comprising at least 90 weight percent, exclusive of water, boehmite, and
calcining the shaped particle under a controlled temperature condition to
convert the boehmite of the shaped particle to gamma-alumina. The
controlled temperature condition is controlled to within a calcination
temperature range of from about 850° F. and 950° F. so that
essentially all of the boehmite of the shaped particle is converted to a
crystalline transitional phase of alumina but less than a material amount
of the boehmite of the shaped particle is converted to a crystalline
transitional phase other than gamma-alumina to thereby provide a calcined
shaped particle. The calcined shaped particle is impregnated with a
hydrogenation catalytic component to thereby provide an impregnated
calcined shaped particle that is calcined to thereby provide the catalyst
composition.

[0016] In accordance with yet another invention is a process for
manufacturing a low sulfur distillate product by contacting under
hydrodesulfurization conditions a middle distillate hydrocarbon feedstock
having a high sulfur concentration with the aforedescribed catalyst or a
catalyst made by the aforedescribed method and yielding a low sulfur
middle distillate product having a low sulfur concentration.

[0017] FIG. 1 presents the X-ray diffraction spectrum for a shaped support
calcined at a calcination temperature of 750° F.

[0018] FIG. 2 presents the X-ray diffraction spectrum for a shaped support
calcined at a calcination temperature of 850° F.

[0019]FIG. 3 presents the X-ray diffraction spectrum for a shaped support
calcined at a calcination temperature of 900° F.

[0020]FIG. 4 presents plots of the reaction temperature required for the
desulfurization of a diesel feed stock under certain test conditions to
yield a diesel product having a 10 ppm sulfur concentration as a function
of catalyst age for an inventive catalyst and for a comparative catalyst.

[0021]FIG. 5 presents a contour plot with each contour line representing
a single sulfur concentration of a desulfurized middle distillate product
resulting from the use of a catalyst made by an embodiment of the
inventive method which uses a carefully controlled heat treatment of the
catalyst support followed by a carefully controlled heat treatment of the
impregnated heat treated catalyst support.

[0022] A novel catalyst composition has been discovered that has a
particularly high activity when used in the hydrodesulfurization of a
hydrocarbon distillate feed stock, such as, for example, diesel oil, that
has a high concentration of sulfur or sulfur compounds such as
organosulfur compounds. This catalyst composition can provide for
significantly improved diesel desulfurization activity when compared to
other known hydrodesulfurization catalyst compositions. It is especially
useful in the manufacture of an ultra-low sulfur diesel product that has
a sulfur concentration of less than 15 parts per million (ppm) and even
less than 10 ppm or less than 8 ppm.

[0023] It has been discovered that the inventive high activity catalyst
composition is a supported catalyst in which a hydrogenation component is
supported on a specially made shaped support that comprises gamma
(γ) alumina. This shaped support can have a material absence of the
transition alumina phases of delta (δ) alumina, theta (θ)
alumina and kappa (κ) alumina. The shaped support further can have
a material absence of aluminum hydrate, and it can even further have a
material absence of aluminum hydrate and transition alumina phases other
than gamma alumina. Thus, the shaped support of the inventive catalyst
composition can comprise gamma alumina and have a material absence of
aluminum hydroxide and forms of transitional crystalline phases of
alumina other than gamma alumina. Indeed, one important embodiment of the
invention is that the shaped support, upon or into which is incorporated
the hydrogenation catalytic component, has a material absence of the
transitional crystalline phases of alumina, such as, for example, alpha
(α) alumina, delta (δ) alumina, eta (η) alumina, kappa
(κ) alumina, and theta (θ) alumina, and additionally, a
material absence of aluminum hydroxide, such as, for example, alpha mono
aluminum monohydrate (boehmite).

[0024] A particularly important aspect of the inventive method for
preparing the catalyst composition includes the use of certain starting
materials and the formation of a shaped particle that is heat treated
under carefully controlled temperature and heat treatment conditions so
as to provide a heat treated shaped particle having the desired
composition required for forming the final catalyst composition having
high activity when used for the desulfurization of a distillate feed
stock. The controlled heat treatment of the shaped particle is followed
by the incorporation of the catalytic component into the heat treated
shaped particle and a second carefully controlled temperature and heat
treatment step.

[0025] The starting material used in preparing the shaped support particle
of the catalyst composition is selected from among aluminum hydroxides,
which are also referred to by those skilled in the art and herein as
alumina hydrate or hydrated alumina, that when prepared and treated in
accordance with the particular features of the inventive preparation
method will provide a heat treated support particle and catalyst
composition having a high hydrodesulfurization activity. Various aluminum
hydroxides are commercially available, but the preferred aluminum
hydroxide for use in preparing the shaped support particle is alpha
alumina monohydrate, which is also referred to as boehmite, having the
chemical formula α-AlO(OH).

[0026] In general, the starting boehmite material used in the preparing
the shaped support particle is in the form of a powder, and it is
particularly desirable for the boehmite material to be a high purity
boehmite with more than 98 percent and even more than 99 percent of the
boehmite material being in the form of alpha alumina monohydrate. It is
also desirable for the boehmite material to contain less than small
amounts of impurities, such as, silicon dioxide (SiO2), iron oxide
(Fe2O3) and alkali (Na2O) and alkaline earth (MgO) metals.
For instance, the silicon dioxide should be present in the boehmite
material at a concentration of less than 200 ppm, and, preferably, less
than 150 ppm. But, typically, the silicon dioxide may be present in the
range of from 80-130 ppm. The iron oxide should be present in the
boehmite material at a concentration of less than 200 ppm, but,
typically, the concentration may be present in the range of from 50 to
150 ppm. The alkali metal should be present at a concentration of less
than 50 ppm, but, typically, it may be present in the range of from 5 to
40 ppm.

[0027] The shaped support of the starting material may be formed by any
suitable method known to those skilled in the art; provided, that a
shaped particle of the starting support material can be subsequently heat
treated in accordance with the invention to provide a heat treated shaped
support particle having the necessary properties of the invention.
Examples of known shaping methods include tableting, pelletizing, and
extrusion methods.

[0028] It is preferred to use an extrusion method to form the shaped
support particle. To make the shaped support particle by this method, the
starting aluminum hydroxide material is mixed with water and, if
required, a suitable acid compound, in proportions and in a manner so as
to form an extrudable paste suitable for extruding through an extrusion
die to thereby form an extrudate. Generally, the weight ratio of aluminum
hydroxide-to-water mixed together to form the extrudable paste is in the
range of from 0.1:1 to 10:1, but, more typically, the weight ratio of
aluminum hydroxide-to-water is in the range of from 0.5:1 to 5:1. The
preferred weight ratio of aluminum hydroxide-to-water used to form the
extrudable paste is in the range of from 0.75:1 to 3:1, and, most
preferred, it is in the range of from 1:0 to 2:0.

[0029] The acid compound added to the mixture of aluminum hydroxide and
water can be any suitable acid that assists in the formation of a
suitable extrudable paste, and it is generally used to control the pH of
the mixture to within the range of from 3 to 7. Strong mineral acids,
such as nitric acid, may be used, but the preferred acid is acetic acid.

[0030] The formed extrudate used as the shaped support particle of the
invention may have any cross-sectional shape such as cyclinderical
shapes, polylobal shapes or any other suitable shape. A typical size of
extrudate has a cross-sectional diameter in the range of from about 1/10
inch to 1/32 inch and a length-to-diameter ratio in the range of from 2:1
to 5:1. The preferred shape is a tri-lobe.

[0031] It is an important aspect of the method of preparing the shaped
support particle and the final catalyst composition of the invention for
the shaped support particle to substantially entirely comprise aluminum
hydroxide, exclusive of the water content. The preferred form of the
aluminum hydroxide is boehmite, and especially preferred is high purity
boehmite. Thus, the shaped particle will comprise at least 90 weight
percent aluminum hydroxide, wherein the weight percent is based upon the
dry weight of the shaped support particle, i.e., the weight percent is
based on the total weight of the shaped support particle exclusive of the
weight of the water contained in the shaped support particle. It is
preferred, however, for the shaped particle to comprise at least 95
weight percent aluminum hydroxide, and, most preferred, the shaped
particle can comprise at least 98 weight percent aluminum hydroxide.

[0032] The shaped support particle is then heat treated under treatment
conditions that include the careful control of the temperature conditions
so as to assure that the resulting heat treated shaped support particle
does not contain undesirable amounts of delta alumina and theta aluminum
and, even, other phases of alumina; and, preferably, so as to assure that
essentially all the aluminum hydrate is converted to an alumina phase,
which is preferably the gamma alumina phase. Therefore, the heat
treatment temperature is controlled during the heat treatment of the
shaped particle to within a specific temperature range to give a heat
treated shaped particle having a material absence of the transition
alumina phases of delta (δ) alumina, eta (η) alumina, theta
(θ) alumina and kappa (κ) alumina. Through the carefully
controlled heat treatment of the shaped support it further can have a
material absence of aluminum hydroxide, and even a material absence of
aluminum hydroxide and a material absence of transition alumina phases
other than gamma alumina.

[0033] The temperature at which the heat treatment is conducted is
controlled to within a narrow range and for a heat treatment time period
so as to provide the heat treated shaped particle that has the properties
as described herein. The temperature during the heat treatment be can
controlled to within the range of from about 850° F. to about
950° F. for a heat treatment time period in the range of from
about 0.5 hours to about 72 hours or even a longer time period as is
required to provide the necessary conversion of the starting aluminum
hydroxide material to the desired alumina phase. More specifically, the
controlled temperature condition is controlled so that the heat treatment
temperature does not exceed 940° F. so as to minimize the
conversion of the starting aluminum hydroxide material to the undesirable
delta alumina, eta alumina, theta alumina, kappa alumina, and alpha
alumina phases. It is preferred for the controlled heat treatment
temperature to not exceed 920° F., and, most preferred, the
controlled heat treatment temperature should not exceed 910° F. In
order to provide for the required conversion of the starting aluminum
hydroxide material to the desirable alumina phase of gamma alumina, the
controlled heat treatment temperature should exceed 850° F., and,
preferably, the controlled heat treatment temperature should exceed
875° F. Most preferably, the controlled heat treatment temperature
should exceed 890° F.

[0034] What is meant when referring herein to the "material absence" of a
particular component of the heat treated shaped particle is that the
relevant component is not present therein in an amount that significantly
affects the ultimate catalytic properties of the final catalyst
composition of the invention. It is believed that the significant
presence of various phases of alumina other than gamma alumina and of
aluminum hydrate in the heat treated shaped particle used to make the
final catalyst composition can have a negative impact on the diesel
hydrodesulfurization activity of the final catalyst composition. Thus,
while small amounts of the alumina phases other than gamma alumina and of
aluminum hydrate may be present in the heat treated shaped particle used
in the preparation of the final catalyst composition, such amounts should
be insignificant so that they do not materially negatively affect the
activity of the final catalyst. But, in any event, less than 5 weight
percent of the alumina of the heat treated shaped particle is in a
crystalline alumina phase other than gamma alumina, such as the alumina
phases of delta alumina, theta alumina, eta alumina, kappa alumina and
alpha alumina, and preferably less than 2 weight percent, and, most
preferably, less than 1 weight percent, of the alumina of the heat
treated shaped particle is in a crystalline transitional phase other than
gamma alumina.

[0035] It is also an important aspect of the invention that the heat
treated shaped particle contain a material absence of aluminum hydroxide.
Therefore, a substantial portion of the aluminum hydroxide contained in
the shaped particle prior to its heat treatment should be converted by
the heat treatment to a crystalline phase of alumina, preferably, gamma
alumina. The heat treated shaped particle, thus, should contain an
insubstantial amount of aluminum hydroxide, for instance, less than 5
weight percent based on the total weight of the heat treated shaped
particle. Preferably, the heat treated shaped particle contains less than
2 weight percent, and, most preferably, less than 1 weight percent
aluminum hydroxide.

[0036] The heat treated shaped particle has a specific pore structure
including a characteristic median pore diameter, total pore volume and
pore size distribution. Generally, the median pore diameter of the heat
treated shaped particle is in the range of from about 70 angstroms to 120
angstroms, but, preferably, the median pore diameter is in the range of
from 80 angstroms to 110 angstroms. More preferably, the median pore
diameter of the heat treated shaped particle is in the range of from 90
angstroms to 100 angstroms.

[0037] The total pore volume of the heat treated shaped particle is
generally in the range of from about 0.5 cubic centimeters per gram
(cc/gram) to about 1.1 cc/gram. Preferably, the total pore volume is in
the range of from 0.6 cc/gram to 1 cc/gram, and, most preferably, from
0.7 cc/gram to 0.9 cc/gram.

[0038] The percentage of the total pore volume contained in the pores of
the heat treated shaped particle having a pore diameter less than 80
angstroms is less than 25 percent and, among these pores, less than 3
percent of the total pore volume of the heat treated shaped particle is
in the pores having a diameter smaller than 50 angstroms. As for the
pores having a diameter between 80 angstroms to 350 angstroms, more than
70 percent of the total pore volume of the heat treated shaped particle
is contained in such pores. It is preferred, however, for at least 75
percent, and, most preferred, at least 80 percent, of the total volume to
be in the pores having a diameter between 80 to 350 angstroms. Less than
3 percent of the total pore volume of the heat treated shaped particle is
in the pores having a pore diameter greater than 350 angstroms.

[0039] The references herein to the pore size distribution and pore volume
of the alumina support material are to those properties as determined by
mercury penetration porosimetry. The measurement of the pore size
distribution of the alumina support material is by any suitable
measurement instrument using a contact angle of 140° with a
mercury surface tension of 474 dyne/cm at 25° C.

[0040] Following the formation of the heat treated shaped particle, the
catalytic components are incorporated into the heat treated shaped
particle, which is thereafter subjected to a second heat treatment,
again, under carefully controlled heat treatment conditions so as to
assure that an insignificant amount of the alumina support is converted
to undesirable crystalline alumina phases. Any suitable means or method
may be used to incorporate the catalytic components into the heat treated
shaped particle, but any of the known impregnation methods, such as,
spray impregnation, soaking, multi-dip procedures, and incipient wetness
impregnation methods, are preferred. The catalytic components include
hydrogenation catalytic components such as those selected from Group 6 of
the IUPAC Periodic Table of the Elements (e.g. chromium (Cr), molybdenum
(Mo), and tungsten (W)) and Groups 9 and 10 of the IUPAC Periodic Table
of the Elements (e.g. cobalt (Co) and nickel (Ni)). Phosphorus (P) is
also a desired catalytic component.

[0041] The catalytic components may be incorporated into the heat treated
shaped particle using one or more impregnation solutions containing one
or more of the catalytic components. The preferred impregnation solution
is an aqueous solution of the desired catalytic component or precursor
thereof. In the case of a Group 9 or 10 metal, Group 9 or 10 metal
acetates, carbonates, nitrates, and sulfates or mixtures of two or more
thereof may be used, with the preferred compound being a metal nitrate
such as nitrates of nickel or cobalt. In the case of a Group 6 metal, a
salt of the Group 6 metal, which may be a precursor of the metal oxide or
sulfide, may be used in the impregnation solution. Preferred are salts
containing the Group 6 metal and ammonium ion, such as ammonium
heptamolybdate and ammonium dimolybdate. The concentration of the metal
compounds in the impregnation solution is selected so as to provide the
desired metal concentration in the final catalyst composition of the
invention. Typically, the concentration of the metal compound in the
impregnation solution is in the range of from 0.01 to 100 moles per
liter.

[0042] The amounts of catalytic metal compound and, if desired,
phosphorous compound, incorporated or impregnated into the heat treated
shaped particle is such that when the impregnated, heat treated shaped
particle is subsequently subjected to a heat treatment, the final
catalyst composition of the invention has the desired concentrations of
the catalytic components. The amount of Group 6 metal contained in the
final catalyst composition generally should be in the range of from about
3 to about 30, preferably from 4 to 27, and, most preferably, from 5 to
20 weight percent, calculated as a Group 6 metal trioxide and based on
the total weight of the final catalyst composition inclusive of the
catalytic components. The amount of Group 9 or 10 metal contained in the
final catalyst composition generally should be in the range of from about
0.01 to about 10, preferably from 0.1 to 8, and, most preferably, from 1
to 6 weight percent, calculated as a Group 9 or 10 metal monoxide and
based on the total weight of the final catalyst composition inclusive of
the catalytic components. If the final catalyst contains a phosphorous
component, it is present at a concentration in the range of from about
0.01 to about 5 weight percent, calculated as phosphorous.

[0043] The heat treatment of the impregnated heat treated shaped particle,
as in the heat treatment of the shaped particle, is also conducted under
carefully controlled heat treatment temperature conditions so as to
assure that an insignificant portion of the alumina therein is converted
to the undesirable crystalline transitional phases of alumina. Indeed,
one embodiment of the invention includes the combined use of specific
heat treatment conditions for each of the two heat treatment steps to
provide the final catalyst having unexpectedly better middle distillate
hydrodesulfurization catalytic performance. It has been found that an
unexpected improvement in the desulfurization performance of the final
catalyst is achieved when the temperature conditions of the second heat
treatment step shifted to somewhat higher temperatures than those used in
the first heat treatment step.

[0044] A final catalyst having especially good middle distillate
desulfurization properties is obtained when the temperature range of the
first heat treatment step to yield the heat treated particle is, as
discussed above, from about 850° F. to about 950° F. and
the temperature range of the second heat treatment step to yield the
final catalyst is from about 870° F. to about 1000° F. A
preferred temperature range at which the second heat treatment step is
conducted is from 880° F. to 990° F., and, most preferred,
from 900° F. to 980° F. The second heat treatement step is
conducted for a time period necessary to provide the desired final
catalyst composition and can generally be in the range of from about 0.5
hours to about 72 hours. Relative to the upper temperature limit for the
first heat treatment step, the upper limit for the temperature for the
second heat treatment step should be no more than about 35° C.
(63° F.) above the upper temperature limit of the first heat
treatment step, and, preferably, it is no more than 30° C.
(54° F.). Most preferably, the upper temperature limit for the
second heat treatment step in which the impregnated heat treated shaped
particle is heat treated is no more than 25° C. (45° F.) of
the upper temperature limit of the first heat treatment step.

[0045] The final catalyst composition, i.e., the impregnated heat treated
shaped particle that itself has been heat treated, has a specific pore
structure including a characteristic median pore diameter, total pore
volume and pore size distribution. Generally, the median pore diameter of
the final catalyst composition is in the range of from about 80 angstroms
to 110 angstroms, but, preferably, the median pore diameter is in the
range of from 85 angstroms to 105 angstroms. More preferably, the median
pore diameter of the final catalyst composition is in the range of from
90 angstroms to 100 angstroms.

[0046] The total pore volume of the final catalyst composition is
generally in the range of from about 0.6 cubic centimeters per gram
(cc/gram) to about 1.1 cc/gram. Preferably, the total pore volume is in
the range of from 0.65 cc/gram to 1 cc/gram, and, most preferably, from
0.7 cc/gram to 0.9 cc/gram.

[0047] The percentage of the total pore volume contained in the pores of
the final catalyst composition having a pore diameter less than 80
angstroms is less than 25 percent and, among these pores, less than 3
percent of the total pore volume of the final catalyst composition is in
the pores having a diameter smaller than 50 angstroms. As for the pores
having a diameter between 80 angstroms to 350 angstroms, more than 70
percent of the total pore volume of the final catalyst composition is
contained in such pores. It is preferred, however, for at least 75
percent, and, most preferred, at least 80 percent, of the total volume to
be in the pores having a diameter between 80 to 350 angstroms. Less than
3 percent of the total pore volume of the final catalyst composition is
in the pores having a pore diameter greater than 350 angstroms.

[0048] The catalyst composition of the invention is particularly suitable
for use in a process for the hydrodesulfurization of a middle distillate
hydrocarbon feed stock, having a concentration of sulfur or sulfur
compounds, in order to make a low sulfur middle distillate hydrocarbon
product. More specifically, the catalyst composition may be used in a
process for the manufacture of an ultra-low sulfur diesel product having
a sulfur concentration of less than 15 ppm, preferably, less than 10 ppm,
and, most preferably, less than 8 ppm.

[0049] The middle distillate hydrocarbon feed stock as referred to herein
is intended to include refinery hydrocarbon streams having boiling
temperatures at atmospheric pressure in the range of from about
140° C. (284° F.) to about 410° C. (770° F.).
These temperatures are approximate initial and final boiling temperatures
of the middle distillate. Examples of the refinery streams intended to be
included within the meaning of middle distillate hydrocarbon include
straight run distillate fuels boiling in the referenced boiling range,
such as, kerosene, jet fuel, light diesel oil, heating oil, and heavy
diesel oil, and the cracked distillates, such as FCC cycle oil, coker gas
oil, and hydrocracker distillates. The preferred feedstock of the
inventive process is a middle distillate boiling in the diesel boiling
range of from about 140° C. (284° F.) to about 400°
C. (752° F.).

[0050] The sulfur concentration of the middle distillate feedstock can be
a high concentration, for instance, being in the range of upwardly to
about 2 weight percent of the middle distillate feedstock based on the
weight of elemental sulfur and the total weight of the middle distillate
feedstock inclusive of the sulfur compounds. Typically, however, the
middle distillate feedstock of the inventive process has a sulfur
concentration in the range of from 0.01 wt. % (100 ppm) to 1.8 wt. %
(18,000 ppm). But, more typically, the sulfur concentration is in the
range of from 0.1 wt. % (1000 ppm) to 1.6 wt. % (16,000 ppm), and, most
typically, from 0.18 wt. % (1800 ppm) to 1.1 wt. % (11,000 ppm). It is
understood that the references herein to the sulfur content of the
distillate feedstock are to those compounds that are normally found in a
distillate feedstock or in the hydrodesulfurized distillate product that
contain a sulfur atom and generally include organosulfur compounds.

[0051] The final catalyst of the invention may be employed as a part of
any suitable reactor system that provides for the contacting of the
catalyst with the middle distillate feedstock under suitable
hydrodesulfurization reaction conditions that include the presence of
hydrogen and an elevated total pressure and temperature. Such suitable
reactor systems can include fixed catalyst bed systems, ebullating
catalyst bed systems, slurried catalyst systems, and fluidized catalyst
bed systems. The preferred reactor system is that which includes a fixed
bed of the inventive final catalyst composition contained within a
reactor vessel equipped with an reactor feed inlet means, such as a feed
inlet nozzle, for introducing the feedstock into the reactor vessel, and
a reactor effluent outlet means, such as an effluent outlet nozzle, for
withdrawing the reactor effluent or the low sulfur distillate product
from the reactor vessel.

[0052] For the desulfurization of a diesel feedstock, having a sulfur
concentration, the hydrodesulfurization reaction temperature is generally
in the range of from about 200° C. (392° F.) to 420°
C. (788° F.). The preferred hydrodesulfurization reaction
temperature is in the range of from 260° C. (500° F.) to
400° C. (752° F.), and, most preferred, from 320° C.
(608° F.) to 380° C. (716° F.). It is recognized
that one of the unexpected features of the use of the inventive catalyst
composition is that it has a higher hydrodesulfurization activity than
certain conventional catalysts, and, thus, will in general provide for a
comparatively lower process temperature than such conventional catalysts.

[0053] The inventive process generally operates at a hydrodesulfurization
reaction pressure in the range of from about 100 psig to about 2000 psig,
preferably, from 275 psig to 1500 psig, and, most preferably, from 290
psig to 1000 psig. The flow rate at which the distillate feedstock is
charged to the reaction zone of the inventive process is generally such
as to provide a liquid hourly space velocity (LHSV) in the range of from
about 0.1 hr-1 upwardly to about 10 hr-1. The term "weight
average space velocity", as used herein, means the numerical ratio of the
rate at which the distillate feedstock is charged to the reaction zone of
the process in volume per hour divided by the volume of catalyst
composition contained in the reaction zone to which the distillate
feedstock is charged. The preferred LHSV is in the range of from 0.1
hr-1 to 250 hr-1, and, most preferred, from 0.5 hr-1 to 5
hr-1.

[0054] The hydrogen treat gas rate is the amount of hydrogen charged to
reaction zone with the distillate feedstock. The amount of hydrogen
relative to the amount of distillate hydrocarbon feedstock charged to the
reaction zone is in the range upwardly to about 10,000 cubic meters
hydrogen per cubic meter of distillate hydrocarbon feedstock.

[0055] The desulfurized middle distillate product yielded from the process
of the invention has a low or reduced sulfur concentration relative to
the high sulfur concentration of the middle distillate feedstock. One
particularly advantageous aspect of the inventive process is that it is
capable of more economically providing for a deeply desulfurized diesel
product or an ultra low sulfur diesel product. The low sulfur middle
distillate product can have a sulfur concentration that is less than 25
ppm. The ultra low sulfur diesel product can have a sulfur concentration
that is less than 15 ppm. Preferably, the low sulfur middle distillate
product and ultra low sulfur diesel product has a sulfur concentration of
less than 10 ppm, and, most preferably, less than 8 ppm.

[0056] The following examples are presented to further illustrate the
invention, but they are not to be construed as limiting the scope of the
invention.

EXAMPLE 1

[0057] This Example 1 describes the preparation of the alumina support
used in the making of the final catalyst composition of the invention.
The alumina support was calcined at various calcination temperatures in
order to determine the effect that calcination temperature has on the
properties of the calcined support used to make the final catalyst
composition of the invention and upon the catalytic performance of the
final catalyst composition of the invention.

[0058] The shaped support was prepared first by dissolving 150 parts by
weight Ni(NO3)2. 6H2O in 52 parts by weight deionized
water with heating to form a nickel nitrate solution. The nickel nitrate
solution was mixed with 3000 parts by weight (on dry basis) of wide pore
alumina and 30 parts by weight Superfloc 16 extrusion aid using a muller
mixer. The components were mixed for a sufficient period of time to
provide an extrudable paste. The resulting paste was extruded through 1.3
mm extrusion dies to form extrusion particles of the shaped support.

[0059] A 700 gram sample of the shaped support was calcined at a
temperature of 750° F. in a muffle furnace for a time period of
two hours to thereby provide a calcined shaped support (Sample A).

[0060] 700 gram sample of the shaped support was calcined at a temperature
of 850° F. in a muffle furnace for a time period of two hours to
thereby provide a calcined shaped support (Sample B).

[0061] A 700 gram sample of the shaped support was calcined at a
temperature of 900° F. in a muffle furnace for a time period of
two hours to thereby provide a calcined shaped support (Sample C).

[0062] Presented in Table 1 are certain of the physical properties of the
calcined samples described above. Presented in Table 2 is the pore size
distribution as determined by mercury porosimetry of the calcined
samples.

[0063] FIGS. 1, 2 and 3 each presents the X-ray diffraction spectrum for
each of the samples of shaped support calcined at the different
temperatures (i.e., Sample A, Sample B and Sample C). As may be observed
from the spectra of the figures, the spectrum of Sample C (FIG. 3)
indicates that it has no significant amount of boehmite present; however,
the spectra for Samples A (FIG. 1) and B (FIG. 2) indicate that they both
contain a significant amount of boehmite. Also, the spectrum of Sample C
indicates that it is predominantly gamma alumina with little, if any,
amounts of other phases of alumina being present.

EXAMPLE 2

[0064] This Example 2 describes the preparation of catalyst compositions
using the calcined samples described in Example 1. These catalyst
compositions were used in the hydrodesulfurization activity tests
presented in the following Example 3.

[0065] The catalyst compositions were prepared by impregnating the samples
of Example 1 with an impregnation solution followed by drying the
impregnated samples and calcination of the dried, impregnated samples.
The impregnation solution was prepared by combining within a container
vessel 34 parts by weight molybdenum trioxide (MoO3), 8 parts by
weight of 86.1% phosphoric acid (H3PO4), and 77 parts by weight
deionized water. The mixture was heated to 180° F. followed by the
addition of 9 parts by weight cobalt hydroxide (Co(OH)2). The
solution was then heated to 212° F. followed by the addition of 4
parts by weight citric acid monohydrate. The container was then covered
and the solution was heated until it became clear. The container was then
uncovered and the solution was heated to reduce the volume thereof.

EXAMPLE 3

[0066] This Example 3 describes the experimental procedure used to measure
the performance of certain catalyst compositions prepared as described in
the above Examples 1 and 2 in the hydrodesulfurization of a diesel
feedstock having a high concentration of sulfur (1.6 wt. %).

[0067] A laboratory stainless steel isothermal tube reactor, having a
nominal diameter of 3/4 inch, was packed with a 100 cc volume of the
relevant catalyst. As a part of the startup of the reactor, the catalyst
was presulfided by adding 68 grams of TNPS to 1000 grams of the
feedstock. The feed was introduced to the reactor at a rate so as to
provide an LHSV of 1 hr-1, and hydrogen was introduced at a rate of
19.6 liters/hr. The reactor temperature was ramped up over a 5 hour
period to 400° F. and held at 400° F. for a period of 4
hours. Thereafter, the temperature was ramped up to 650° F. over a
4 hour period and then held at 650° F. for two hours. After the
catalyst was presulfided, the feed to the reactor was switched to an
unspiked feedstock. The feedstock used was a straight run gas oil
containing 1.6 weight percent sulfur having ASTM D2887 distillation as
presented in the following Table 3.

[0068] The reactor was operated at a pressure of 300 psig, the feed rate
was adjusted to provide a liquid hourly space velocity of 0.5, and the
hydrogen gas feed rate was 1200 standard cubic feed per barrel of feed
(based at 60° F.). The reactor temperature was adjusted so as to
provide an ultra low sulfur diesel product having a sulfur concentration
of 10 ppmw.

[0069]FIG. 4 presents plots of the reaction temperature required for the
desulfurization of the gas oil feedstock to yield a product having a
sulfur concentration of 10 ppmw as a function of the age for a
representative inventive catalyst and for a comparative catalyst. As can
be seen from the plots, the inventive catalyst demonstrates a
significantly higher hydrodesulfurization activity than does the
comparative catalyst by requiring a lower hydrodesulfurization
temperature, which in some cases is as much as 20° F. to
30° F. lower.

EXAMPLE 4

[0070] This Example 4 describes, in general, the approach used to develop
a prediction model for predicting the sulfur concentration of a
desulfurized middle distillate feedstock obtained using various catalysts
prepared generally in accordance with the method as described in Example
2.

[0071] Final catalyst compositions were made using supports prepared as
described in Example 1 that were calcined at different temperatures
ranging from 750° F. to 1100° F. These supports were
impregnated with catalytic components followed by drying and then
calcining the impregnated support material at different temperatures
ranging from 750° F. to 1050° F. Each of the compositions
was tested for its ability to desulfurize a middle distillate feedstock
having a high sulfur concentration.

[0072] A graphical representation of the results of this study is
presented in the contour plot of FIG. 5. The X-axis of the contour plot
is the temperature at which the support material used in the preparation
of the final catalyst was calcined, and the Y-axis is the temperature at
which the impregnated calcined support material was calcined. Each
contour line represents a sulfur concentration of the desulfurized middle
distillate feedstock resulting from the use of a final catalyst
composition prepared using the inventive two-step heat treatment method
at the two different calcination temperatures. The contour lines are a
best fit of a number of data points used to generate the contour plot.

[0073] As illustrated by the contour plot, the best performing catalysts,
based on their properties for middle distillate desulfurization, are
those prepared using a support material calcined at a calcination
temperature in the range of from about 850° F. to 1000° F.,
which the calcined support material has been impregnated, dried and
calcined at a temperature in the range of from about 880° F. to
1000° F.

[0074] It is understood that while particular embodiments of the invention
have been described herein, reasonable variations, modifications and
adaptations thereof may be made that are within the scope of the
described disclosure and the appended claims without departing from the
scope of the invention as defined by the claims.

Patent applications by Opinder Kishan Bhan, Katy, TX US

Patent applications by SHELL OIL COMPANY

Patent applications in class With specific porosity or pore volume

Patent applications in all subclasses With specific porosity or pore volume